Uplink connects SIP protocol VoIP calls to the proprietary Skype phone network. It works in both directions. The SIP protocol has become the industry standard for VoIP. Thousands of telephone companies, IP phone manufacturers and virtual IP based PBX systems use this protocol to connect calls. The problem is the proprietary IP phone 'Skype' has an almost cult following in the youth market and sometimes the call rates for SkypeOut are discounted. This software lets you connect calls between the two systems.